I usually carry a 357 when (shotgun) hunting, and either a 357 or 9mm when hiking. If it's a very public trail, I often lean towards the 9mm as I think they conceal better and are a little comfier to carry.
Mountain lions are the biggest creature we have to deal with, though I think I'd rather run into a kitty than a pack of javelina when the dogs are along. Is a 357 better for pumers? Probably, but everything is a compromise.
I picked up a jackass rig on the cheap this year to shoulder carry the 9mm (I really really don't like a gun on my hip for any serious hiking) but don't know how often I'll get to use it because it's seldom cool enough here for a decent cover garment.
But to answer the question, I think you can make do with a 9mm nicely. Some people just shoot semis better than revolvers too, don't know if that applies in this case.
